Urinary tract stones include calculi existing in a urinary tract such as a kidney, a ureter, a bladder, a urethra and the like. A calculus generated in a kidney or in a ureter is referred to as an upper urinary tract stone. In urinary tract stone disease, various symptomatic states are caused by these urinary tract stones. For example, when a calculus generated in a kidney is moved to a ureter, the calculus injures the ureter and causes a pain or blood in the urine. The calculus may also block the ureter, so that an evanescent hydronephrosis state is generated, and hence an acute pain (colic pain) from a lower back to a lateral region may result. Therefore, in order to alleviate or treat these symptoms, removal of the calculi is considered to be effective.
Among methods of removing calculi existing in an upper urinary tract, a transurethral ureterolithotripsy (TUL or URS), an extracorporeal shock wave lithotripsy (ESWL), and a percutaneous calculus lithotripsy (PCNL or PNL) are known as a surgical positive method of removal. Examples of the TUL include an r-TUL (or r-URS) in which a rigid uretero-reno fiberscope (or a rigid ureteroscope) is used, and an f-TUL (or f-URS) in which a flexible uretero-reno fiberscope (or a flexible ureteroscope) is used. Among these methods, the TUL generally is a therapeutic approach using an uretero-reno fiberscope (or an ureteroscope), and including reaching calculi existing in a ureter or renal pelvis and renal calyx extracorporeally, transvesically, or ureterily, directly breaking the calculi, and extracting the stones. The TUL has a higher stone free rate in comparison with ESWL or PCNL, and gives less damage to the ureter, thereby having an advantage of being less invasive. In particular, such an advantage is significant in the f-TUL.
In the TUL, stone breaking and extraction of the stones are performed via an instrument channel of the rigid ureteroscope or the flexible ureteroscope. The stone breaking is generally performed by using a laser fiber such as Holmium:YAG (Ho:YAG) laser or the like. The extraction of the stones is generally performed by using a basket catheter (basket forceps). Known examples of the basket catheter include a medical instrument as disclosed in JP-T-2001-512355.
However, the extraction of the stones using the basket catheter of the related art is limited by the gripping function of the basket catheter, the size of a ureteral inner cavity or the size of a ureteral access sheath (guiding catheter). Hence, only a small amount of the calculus and calculi broken pieces can be removed at one time. Often removal requires a series of stone extracting operations to remove the pieces one by one, from a step of gripping the broken calculus pieces to a step of carrying the gripped broken calculus pieces to the outside of the body with the basket catheter. Therefore, in order to remove the calculus, it is necessary to perform an insertion and retraction operation of the basket catheter many times between the outside of the body and the position where the calculus exists. Accordingly, a user (operator) bears a heavy burden. In addition, various disadvantages for a patient occurs due to an elongation of an operation time for performing the insertion and retraction operation of the basket catheter many times such as an increased probability of infection of the urinary tract after the operation or the like, a development of burden to a ureter due to ischemia or the like, and an increased risk of relapse because of a failure of removal of the calculi and the broken calculus pieces within a limited time of operation set for suppressing infection or the like following a surgical procedure.
The basket catheter used in the related art generally has a difficulty to grip calculi or broken pieces having small diameters. In contrast, a basket catheter developed for collecting the small diameter calculi or broken pieces generally has difficulty gripping calculi having large diameters, causing insufficient operability. In addition, a method of breaking calculi or the broken pieces into sand-like diameters (i.e., very small pieces) so that natural stone drainage by a urine flow is expected is proposed. However, this method requires labor and time for breakage and, in addition, requires preparation of a specific laser output apparatus in many cases. Therefore this method is not practical and cost-effective for widespread use at the moment.
The basket catheter has difficulty collecting the calculi and broken pieces which are located positions difficult for the forceps to access, such as corners of minor calyx, side of renal papilla or the like. Consequently, in the method of the related art using the basket catheter, it is difficult to improve the stone free rate, and is difficult to reduce the relapse rate.
In addition, by gripping a plurality of calculi and the broken pieces, end surfaces of the calculi are exposed by a gap between the metallic wires that are part of the basket forceps. Therefore, if an attempt is made to remove the plurality of calculi and the broken calculus pieces to the outside of the body at once, inner walls or the like of the kidney and the ureter may become damaged. Another problem arises when exposed portions of the calculi fit into (i.e., are lodged in) an end surface of an opening of an ureteral access sheath on a far side and hence cannot be pulled out to the outside of the body. In such a case, the basket catheter is forced to be discarded.